Steam boiler



Aug. 7, 1934. H. J. KERR 1,969,406

STEAMBOILER Filed April 15, 1932' 2 Sheets-Sheet 1 Fig 7] INVENTOR Howard J flier! EEQKW ATTORNEY v v Aug. 7, 1934. H. J. KERR 1,969,406

- STEAM BOILER Filed April 13, 1932 2 Sheets-Sheet 2" Fi TZ Fig INVENTOR Howard J if err ATTORNEY Patented Aug. 7, 1934 :VUNITEDI STATES PATENT 'oFE-icafj Howard J. Kerr, Westfield, N. J., assignor to The Babcock & Wilcox Company, Bayonne, N. J., a a corporation of New Jersey Application April 13, 1932, Serial'No. 604,978 8' Claims. (01. 122-299)- ;My present invention relates in general to the construction and operation of water tube steam boilers. Inthe usual arrangement of the steam boiler units of a; central station of large capacity and subjecttorvarying steam, loads during the normal dailyoperation, a certain portion of the unitsare used to carry the base load, while other units are thrown on the line to pick up and carry the peak loads. The operating schedule and con- :10 ditions of 'base' and peak load boilers are quite different and -to attain the maximum operating efficiency in each type of boiler; substantial differences'in design are usually necessary. Base load boiler units are usually characterized by substantially constant rates of fuel, air and water supplythereto.

The present invention-is especially intended for use in a two-stage water tube boilerin which the rate of flow of feed water through the primary or forced circulation steam generating stage normally remains above a' predetermined value. The object of my invention is the provision of a water tube boiler of the general character described witha-highly compact and thermally efiicient arrangement of the fluid conduit elements constitutin'g'the forced circulation steam generating stage.

The various features of novelty which characterlze'my invention are pointed out with particularity'in the claims annexed to and forming; a

part of this specification. For a better understanding of the invention, its operating advan' tages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described preferred embodiments of my invention.

Of the drawings, Fig. l is a sectional elevation, partly diagrammatic of awater tube boiler constructed in accordance with my, invention; Fig. 2

is-a. sectional elevation of a. portion of the boiler shown in "Fig. '1 illustrating a modified arrangement .of the'heating surface; and Fig. 3 is an enlarged view partly in section of a-portion of the {1,5 construction shown in Fig. 2.

'50 burned by an underfeed stoker 11. ,The upper end of the furnace chamber'is substantially in alignment'with' the lower end of a verticalheating gas pass :12. A relatively shallow bank of natural circulation steam: generatingtubular elements 13 '55 :is'positioned across thelower end Of t e gas p 12. The tubes 13 receive preheated water from a transversely extending steam and Waterdrum 14 located at a vertical distance above the highest point of steam generation in the tubebahk13 which is great as compared to'the vertical Idist'ance between the highest and lowestpoi'nts of steam generation in the tube bank. Downtake circulators 15 connect the bottombf the .drum 14 to downtakeheaders 16 at the lower endsof the tubes 13. The steam generated in the tubes. 13 passes through uptake headers 1'7 and uptake circulatorslS to the drum 14. y M A;

A vertical wall 19, having a lower offset portion 20 through whichthe downtake circulators pass,

extends vertically from the downtake headers 16 to a damper controlled heating gas outlet 21. at the upper end of the'gas pass. The opposite-Wall 22 of the gas pass is inclined verticallyrfrom vthe uptake headers 1'7 towards the wall 19 until the gas outlet 21 is reached. The uptake circulators 18 line thewall 22 throughout its extent, andhave horizontal portions 18 extendingracrossthe gas pass directly below the gas outlet 2I; V a

As above described the construction has only a small portion of the gas pass occupied bythe tube bank 13. The remaining portion of the'gas pass .is advantageously utilized for a compact i and thermally eificient arrangement therein of a convection heated 'superheater and a steaming-economizer. return bend tubes-23 arranged inpara'llel vertical planes, and providing parallel flow paths be"- tween the superheater'inlet header 24 and outlet header 25-. a The legs of the tubes 23 are. arranged parallel to the tube bank 13-and between the lower 'end of the wall portion 19 and the tube bank-.,

:is formed in a'plurality of 'superposed horizontal tube legs connected by return bend portions. The available gas pass space is fully utilized by proportioning the lengths of the tube legs to the horizontal extent of the available space. For example, in the economizer section 26,-the lower? Y I most tube leg is quite short, while the remaining tube legs progressively increase in length inaccerdance with the varying horizontal. distance between the wall 19 and the uppermost rowof superheater tubes23, Thetubes of the 800119:-

The superheater consists ofa series of mizer sections 2'7, 28 and 29, located in the tapering portion of the gas pass, have tube legs pro gressively decreasing in length upwardly through these sections.

The economizer sections form part of a forced circulation steam generating stage of the boiler. Feed water is delivered to the tubes of the economizer section 29 through a header 31 by means of a suitable boiler feed pump (not shown) and passes downwardly through the parallel flow paths formed by the tubes 30 into corresponding tubes in the successive economizer sections 28, 27 and 26. Each pair of corresponding tubes in successive sections is connected by a detachable return bend member 32 located externally of the gas pass wall 19. The lowermost tube legs in the economizer section 26 pass through the wall 19 and are connected to an external horizontal drain header 34, provided with a valved drain connection 35. i

In the operation of the boiler described, feed water is supplied at a relatively high rate to the header .31 and flows downwardly through the successive sections through parallel flow paths. The water is gradually heated to the corresponding saturated steam temperature by the heating gases flowing upwardly through the pass and at somepoint in each of the flow paths steam is generated. The point of steam generation in the several flow paths will vary with different conditions of operation. The heating surface in the several economizer sections is desirably so proportioned relative to the heat transfer surface in the superheater 23 and tube bank 13 and to the heat output of the furnace chamber that no steam will be .generated until the sections 27 or 26 have been reached. The steam and water ing lugs 42 welded on the tube return bend portions and circulators 18. The circulators 18 in turn are carried by hangers 43 depending from the steel framework surrounding the upper sections of the boiler and welded to the circulators 18, as indicated.

In operation, the heating gases generated in the furnace chamber 10 pass successively over the natural circulation tube bank, superheater, economizer sections and the horizontal portions 18 of the uptake circulators to the gas outlet 21.

The absence of flow baffles in the single vertical pass avoids the presence of dead gas zones and.

requires only a relatively small amount of fan power because of the low draft loss present in face is arranged in a highly compact manner.

The normal rate of feed water supply to the economizer will eliminate any tendency of the steam generated in the lower sections to rise against the downflowing water. To insure equalization of flow through the parallel flow circuits, flow resistances of the character shown in Fig. 3 may advantageously be incorporated in the tubes 30, preferably at their points of connection to the inlet headers '31.

In the modification illustrated in Fig. 2, a horizontal header 44 is interposed between the discharge ends of the tubes 30a in the economizer section 28 and the inlet ends of the tubes 30b in the section 2'7. The heating surface in this construction is likewise proportioned so that no steam generation will occur except in the sections 27 or 26. The use of flow resistances in the water heating portion of the economizer has been found to be desirable to provide an equalization of the flows through the parallel flow circuits. Such resistances are placed as close to the steam generating zone as possible and in the present construction the header 44 may be advantageously used for this purpose. As shown in Fig. 3, the flow resist; ances are in the form of elongated small diam eter tubes 38 positioned in'the inlet ends ofthe tubes 30b and opening to the header through a closure plug 39, which serves as a support therefor. The tubes 38 are looped to provide a fluid flow through all portionsof the tubes in which they'are located; The header 44 is shown as elevated above the'major portion of the heat ing surface in the section '28'to provide-a trap for any steam that may be generated iii-the sections 26 or 27 during lay-over periods of the boiler. The header 44 receives and mixes the'parallel streams from the upper sections and 'the'flow i resistances incorporated therein will insure that steam generation will occur at substantially the same point in the tubes of the economizer sections therebelow. 1

Certain novel features illustrated and described, but not claimed herein, are disclosed-and claimed in my application, Serial No. 604,9'l7 filed April While in accordance with the provisions-ofthe statutes I have illustrated anddescribed herein the best forms of my invention now known to me, those skilled in the art will understandthat changesmay be made in the form of the apparatus disclosed without departing from the spirit of the invention covered by my claims, and that certain features of my invention may=sometimes be usedto advantage without a corresponding use of other features. 3

I claim: 1. A water tube boiler comprising a furnace chamber, a vertical heating gas pass in communication with said furnace chamber, a natural circulation' bank of steam generatingtubes positioned in the lower portion of said gas-pass, a

steam and water drum positioned above said bank,

uptake and downtake circulators connecting said tube bank and drum, and a forced flow economizer having a fluid flow therein independent of the fluid flow in said natural circulation tube bank and comprising a plurality of superposed economizer sections in said gas pass in the portion thereof bounded by said natural circulation tube bank, uptake and downtake circulators-and drum, means interconnecting said economizer sections and providing a downflow through all of-said superposed economizer sections, a drain header connected to the discharge ends of the tubes in the lowermost section, and, a. conduit connect ing said drain header to said drum.

2. A water tube boiler comprising a jfurnacje chamber, a vertical heating gas pass in ooinniuiii= cation with said furnace chamber, a natural circulation banker steam generating tubes positioned iiithe lower portion 6f said gas pass, a steam and Water dr m pdsitiofied move said bank, hp take and downtake circulators coiinctirlg said tube bank and drum, and a forced flow economizer having a fiuid flow therein independent of the fluid flow in said natural circulation tube bank and comprising a plurality of superposed economizer sections in the portion of said gas pass bounded by said tube bank, uptake and downtake circulators and drum, each section being formed by a series of multiple-loop return bend tubes arranged in parallel, means interconnecting said economizer sections and providing parallel flow paths through each of saidsectionsand a enera 1 eouilte'rcuifreiit flow path through all of and sections, a mixing header interposed between the discharge end of one of said sections and the inlet end of the next section, and a conduit connecting the lowermost section to said drum.

3. A water tube boiler comprising a furnace chamber, a vertical heating gas pass in communication with said furnace chamber, a natural circulation steam generating stage comprising a bank of horizontally inclined tubes extending across said gas pass, a steam and water drum located a substantial distance above said tube bank, uptake and downtake circulators connecting said'tube bank and drum, and a forced flow steam generating stage comprising superposed economizer sections arranged in said gas pass in the portion thereof bounded by said tube bank, uptake and downtake circulators and drum, means interconnecting said economizer sections and providing parallel downflow paths through all of said sections, a mixing header interposed between two of said sections, and the heating surface of said economizer sections being so proportioned and arranged as to avoid the generation of steam in any section prior to said mixing header.

4. A water tube boiler comprising a furnace chamber, a vertical heating gas pass in communication with said furnace chamber, a natural circulation bank of steam generating tubes positioned in the lower portion of said gas pass, a steam and water drum positioned a substantial distance above said bank, uptake and downtake circulators connecting said tube bank and drum, and a forced flow steam generating stage having a fluid flow therein independent of the fluid flow in said natural circulation tube bank and comprising a plurality of superposed water heating and steam generating sections, each formed by a series of return bend tubes arranged in parallel and having parallel tube leg portions extending horizontally across said gas pass in the portion thereof bounded by said natural circulation tube bank, uptake and downtake circulators and drum, means interconnecting said sections and providing parallel downflow paths successively through all of said superposed sections, and a conduit connecting the lowermost section to said drum.

5. A water tube boiler comprising a furnace chamber, a vertical heating gas pass in communication with said furnace chamber, a natural circulation bank of steam generating tubes positioned in said gas pass, a steam and water drum positioned above said bank, uptake and downtake circulators connecting said tube bank and drum, a plurality of superposed economizer sections in the portion of said gas pass above said tube bank, each section being formed by a series of return bend tubes arranged in parallel, means interconnesting said economizer sections and providing parallel flow paths through each of said sections and a eneral jeoiirltercurrent flow path through all (5f sa d sections,- a headerinterposed between the discharge and of a nemstearnmg section and the inlet end or a steaming section, sa d header being at a level above the lowermost tubes of the non-steaming section to which the header is connected, and a conduit connecting the lowermost section to said drum.

, 6. A water tube boiler comprising a furnace chamber, a vertical heating gas pass in communication with said furnace chamber, a natural circulation bank of steam generating tubes positioned in said gas pass, a steam and water drum positioned above said bank, uptake and downtake circulators connecting said tube bank and drum, and a forced flow steam generating stage having a fluid flow therein independent of the fluid flow in said natural circulation tube bank and comprising a plurality of superposed economizer sections arranged in said gas pass above said tube bank, means interconnecting said economizer, sections and providing parallel downflow paths through all of said sections, a header interposed between a non-steaming and a steaming section, and flow resistance elements in the inlet ends of the tubes ofsaid steaming section.

7. A water tube boiler comprising a furnace chamber, a vertical heating gas pass in communication with said furnace chamber, a natural circulation bank of steam generating tubes positioned in said gas pass, a steam and water drum positioned above said bank, uptake and downtake circulators connecting said tube bank and drum, a plurality of superposed economizer sections in the portion of said gas pass above said tube bank, each section being formed by a series of return bend tubes arranged in parallel, means interconnecting said economizer sections and providing parallel flow paths through each of said sections and a general countercurrent flow path through all of said sections, a header interposed between the discharge end of a non-steaming section and the inlet end of a steaming section, said header being at a level above the lowermost tubes of the non-steaming section to which the header is connected, flow resistances in the inlet ends of the tubes of said steaming section, and a conduit connecting said steaming section to said drum.

8. A water tube boiler comprising a furnace chamber, a vertical heating gas pass in communication with said furnace chamber, a. natural circulation bank of steam generating tubes positioned in the lower portion of said gas pass, a steam and water drum positioned a substantial distance above said bank, uptake and downtake circulators connecting said tube bank and drum, and a forced flow steam generating stage having a fluid flow therein independent of the fluid flow in said natural circulation tube bank and comprising a plurality of superposed water heating and steam generating sections, each formed by a series of return bend tubes arranged in parallel and having parallel tube leg portions extending horizontally across said gas pass in the portion thereof bounded by said natural circulation tube bank, uptake and downtake circulators and drum, means interconnecting said sections and providing parallel downflow paths successively through all of said superposed sections, a drain header positioned externally of said gas pass and connected to the discharge end of the lowermost section, and a conduit connecting said header to said drum.

HOWARD J. KERR. 

